Background concentrations and quality reference values for potentially toxic elements in soils of Piauí state, Brazil.

The background concentration of potentially toxic elements (PTE) in soils is influenced by the parent material composition and soil forming processes. The soil natural concentration of PTE is a first step to establish regulatory levels for the monitoring of these elements in soils suspected of contamination. In the present study, we performed a natural background concentration survey of PTE in soils of the Piauí state, Brazil. The study provides the basis for establishing soil quality reference values (QRVs) for a large area (over 251,000 km2) with different pedological features. A total of 262 geo-referenced soil samples (0.0-0.2 m) were collected in areas relatively undisturbed by human activity. The concentrations of Ba, Cd, Co, Cr, Cu, Fe, Mo, Ni, Pb, Sb, V, and Zn were determined by ICP-OES. Univariate statistical methods and multivariate exploratory techniques were used to understand the relationship between soil characteristics, geological features, and PTE concentrations in soils. The mean background concentrations of PTE in the soils were generally lower than those reported in other countries and/or other Brazilian states, and followed the order: Fe > Ba > V > Cr > Cu > Pb > Zn > Ni > Pb > Co > Mo > Sb > Cd. The main factors governing the concentrations of PTE in soils were the parent material and the soil texture. The different geological features in the study area influenced the spatial distribution of PTE and divided the state into three regions presenting low, high, and intermediate values. Given this geological and pedological complexity, we proposed establishing three sets of QRV rather than a single QRV for the whole state to avoid misinterpretation regarding the investigation of areas suspected of contamination. This background concentration survey contains a wealth of information that provides the basis for the soil guideline values in the state and supports future research on the impact of anthropogenic activities in soil contamination.

Soil chemical attributes and initial growth of corn crop by adding domestic and industrial sewage sludge / Atributos químicos do solo e crescimento inicial de milho pela adição de lodos de esgoto doméstico e industrial

In recent decades, organic and/or inorganic nonconventional waste such as sewage sludge, agroindustrial or industrial waste, inorganic waste, steel slag, etc., have become some of the most promising alternatives to commercial fertilizer shortages or rising prices. Hence, the aim was to evaluate morphological changes in corn plants and variations in chemical properties of cohesive Yellow Latosol (Oxisol), after the incorporation of sewage sludge doses from domestic waste and the dairy industry. The experimental units were randomised blocks designed with four repetitions. The treatments consisted of five doses of each sewage sludge incorporated into the soil, that is: Domestic Sewage Sludge (DSS) in doses of 0.0; 3.1; 4.6; 6.1 and 9.2 Mg ha-1 (on a dry basis ), and Industrial Sewage Sludge (ISS) in doses of 0.0; 5.2; 7.8; 10.4 e 15.6 Mg ha-1 (on a dry basis), all equivalent to 0; 100; 150; 200 and 300 kg of total N ha-1. Doses equivalent to 150 - 300 kg total N ha-1 led to greater gains in stem diameter, number of leaves, fresh and dry mass of leaves. Increasing doses of both sewage sludges enable gains in the morphological variables studied, except for root length. Positive linear increments occur in the pH and phosphorus content of soils when the doses of sewage sludge are increased. The exchangeable aluminium and potential acidity are reduced, from the first dose of industrial sewage sludge, with no significant difference for domestic sewage sludge.

Nas últimas décadas a utilização de resíduos orgânicos e/ou inorgânicos não convencionais, como lodo de esgoto, resíduos agroindustriais ou industriais, rejeitos inorgânicos, escórias siderúrgicas, dentre outros, surgem como alternativas promissoras a escassez ou encarecimento dos fertilizantes comerciais. Diante do exposto, objetivou-se avaliar alterações morfológicas em plantas de milho e alterações nos atributos químicos de um Latossolo Amarelo coeso, após a incorporação de doses de lodos esgoto doméstico e da indústria de laticínios. Os experimentos foram instalados em um delineamento em blocos casualizados, com quatro repetições. Os tratamentos consistiram de cinco doses de cada lodo incorporadas ao solo, sendo: Lodo de esgoto doméstico (LD) nas doses de 0,0; 3,1; 4,6; 6,1 e 9,2 Mg ha-1 (em base seca) e Lodo de esgoto industrial (LI) nas doses de 0,0; 5,2; 7,8; 10,4 e 15,6 Mg ha-1 (em base seca), equivalentes a 0; 100; 150; 200 e 300 kg de nitrogênio total ha-1. As doses equivalentes de 150 a 300 kg de N ha-1 propiciaram maiores ganhos de diâmetro de colmo, número de folhas, massa fresca e massa seca de folhas. Aumentos nas doses de ambos os lodos de esgotos propiciam ganhos nas variáveis morfológicas estudadas, exceto para o comprimento de raízes. Incrementos lineares positivos ocorrem no pH e no teor de fósforo dos solos com o aumento das doses de lodos. O alumínio trocável e a acidez potencial são reduzidos, a partir da primeira dose de lodo de esgoto industrial, não havendo diferença significativa para o lodo doméstico.